Capacitors are used to store charge in integrated circuits (ICs) such as in DRAM and SRAM cells. However, the growing demand for increasingly smaller and thus more cost effective semiconductor devices, e.g., with large memory capacities, has pushed the development of miniaturized structures in sub-micron technologies. But such miniaturization has its limits. For example, the size of the capacitor becomes increasingly larger with regard to the circuit itself, thus taking up considerable chip real estate. For example, current solutions for series capacitors connect two independent capacitors at metal levels; however, this arrangement takes more real estate in order to provide improved capacitors. Additionally, a typical capacitor can use a MIM (Metal-Insulator-Metal) structure for dense applications, but the values of these capacitors are reducing with each generation due to lack of area as they are planar capacitors.
Also, in certain applications, the capacitor can become easily disrupted due to radiation or other unwanted external discharging events. By way of example, for certain radiation hardened applications the use of a dual capacitor dual, resistor feedback has been used. These structures, though, take up a considerable amount of real estate, for example. Other applications include a single capacitor and two resistor configuration which is believed to be more robust to exposure to high radiation environments such as space applications. However, this approach places additional requirements on the properties of the capacitor. In particular, both electrodes cannot be contacting any part of the silicon, either diffusion or substrate. If they are in contact, a radiation event will upset the SRAM cell, regardless of where the energetic ions or particles hit the cell. For example, in a radiation environment, electron hole pairs (e.g., carriers of electric charge) will be swept to a voltage potential which, in turn, will disrupt the state of the capacitor.
Accordingly, there exists a need in the art to overcome the deficiencies and limitations described hereinabove.